JP2594935B2 - Sputter film forming method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a method and an apparatus for forming a thin film by sputtering, and more particularly, to applying a film forming material to fine steps, grooves or holes on a substrate surface of a semiconductor device or the like. The present invention relates to a method and an apparatus for forming a sputter film, which are suitable for making a good adhesion.

[Conventional technology]

With high integration of LSI, Al wiring is becoming finer and multi-layered, and it is necessary to form Al around a deep hole and form a film.

As a conventional technique for attaching a film forming material to fine steps, grooves or holes on the substrate surface of a semiconductor device with good precision,
Examples include the cusp magnetic field sputtering method described in US Pat. No. 3,325,394 and the method described in JP-A-60-221563.
In the former method, a sputter electrode and a substrate are disposed so as to face each other, and a kasbu magnetic field is formed between the two by electromagnets engaged with each other. The cusp magnetic field has the effect of increasing the plasma density and increasing the film forming speed. On the other hand, as another film forming method, a bias sputtering method can be used. In this method, a sputter electrode (magnetron type sputter electrode) is opposed to a substrate, a negative bias voltage is applied to the substrate surface while depositing a film material on the substrate, and a part of the ions in the plasma generated on the sputter electrode. Into the substrate surface to form a film. The bias sputtering method is more admirable in the structure of the apparatus than the above-described method of generating a cascade magnetic field, and thus the bias sputtering method has been generally used as a sputtering film forming method. However,
In order to form an effective film by this method, it is necessary to increase the bias voltage applied to the substrate. However, if the bias voltage is increased, the substrate generates heat and the substrate surface is damaged by ion intrusion. For this reason, the technology disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 61-221563 is such that the cathode engaged with the target is constituted by a variable magnetic flux cathode whose magnetic flux density can be controlled, so that the amount of inflowing ions can be increased without increasing the bias voltage. It is.

[Problems to be solved by the invention]

In order to form a film around the substrate surface, it is necessary to increase the amount of ions incident on the substrate. For this purpose, as described above, it is necessary to increase the bias voltage.However, in this method, the plasma confined on the surface of the sputter electrode is applied to the substrate side by applying a negative bias voltage to the substrate surface. When the voltage is low, simply applying a bias voltage to the substrate surface cannot sufficiently improve the plasma density on the substrate surface. When the bias voltage is increased, the above-mentioned problem occurs.

More specifically, when the bias voltage is −100 V, the plasma density on the substrate is about 2 × 10 ¹⁰ cm ⁻³ , and the ion current flowing into the substrate at this time is 0.5 A /
It is about φ125. Under these conditions, it was found that the rotation of Al to the deep-angled hole of 1.0 μm × 1.0 μm was not sufficient. On the other hand, when the bias voltage is increased, Ar
Although the gas amount increased, voids and blisters were generated in the sputtered film, and it was found that the bias voltage was limited to -140 V.

An object of the present invention is to provide a sputter film forming method and apparatus capable of forming a high quality thin film while adhering a film forming material to fine steps, grooves, holes, etc. on a substrate surface without increasing a bias voltage. With the goal.

[Means for solving the problem]

In order to solve the above problem, in the present invention, the sputtering film forming method is set to a predetermined pressure by introducing an inert gas such as Ar gas into a vacuum-evacuated container, and facing the inside of the container. A cusp magnetic field is generated between the target and the substrate, and a first power is applied to the target to generate plasma. The plasma is confined between the target and the substrate by the cusp magnetic field, and the substrate is mounted. A second electric power is applied to the substrate electrode to be placed to generate a bias potential on the surface of the substrate, and the target is sputtered by plasma confined between the target and the substrate by a cusp magnetic field, and a film is formed on the substrate while bias is applied. It is performed by letting ions from plasma into the surface of a substrate on which a film is formed from plasma, introducing a gas between the substrate and the substrate electrode, and cooling the substrate on which the film is formed. It was.

Further, according to the present invention, a sputter film forming apparatus includes: a vacuum container means having a vacuum exhaust unit and a gas introduction unit; a target means having a target surface to be sputtered inside the vacuum container means; A substrate electrode means for placing and holding a substrate to be processed in opposition to the target surface, generating plasma by applying first power to the target means, and sputtering the target surface to form a film on the substrate to be processed A cusp magnetic field formed between the target surface and the substrate to be processed held by the first power application means and the target means side and the substrate electrode means side; A magnetic field generating means for confining the plasma in the magnetic field, and a bias electric potential generated on the surface of the substrate to be processed by applying the second power to the substrate electrode means, from the plasma confined by the cusp magnetic field. Second power application means for turning on the surface of the substrate to be processed during film formation; and substrate to be processed during film formation while introducing a gas between the substrate to be processed and the substrate electrode means so as to make ions incident. And a gas introduction means for cooling.

(Operation)

A high-density plasma is generated from the sputter electrode to the vicinity of the sample surface by the formation of the cusp magnetic field. In addition, independently of the cusp magnetic field, a negative low bias voltage or the like that does not cause a film defect on the sample surface is applied to draw high-density ions in the plasma toward the sample substrate. Thereby, the ion current flowing into the substrate can be improved, and the mobility of sputtered particles adhering to the surface of the sample substrate on the substrate surface can be improved. As a result, the spread of the sputtered material on steps, grooves, holes, and the like can be improved. Further, the film quality can be kept constant by controlling the temperature of the sample substrate to a constant temperature.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a sputter electrode 4 is attached to an opening 2 above a vacuum vessel 1 with an insulator 3 interposed therebetween, and a target 5 made of a sputter deposition material is attached to the sputter electrode 4 on the vacuum vessel 1 side. A target coil 6 and a yoke 7 for covering the target coil 6 are provided on the atmosphere side. A target coil power supply 23 is connected to the target coil 6. The yoke 7 is for increasing the leakage magnetic flux density generated by the target coil 6. A sputter power source 20 is connected to the sputter electrode 4. An anode 28 is provided on the outer periphery of the target 5 with a gap where no discharge occurs from the target 5, and the anode 28 is fixed to the vacuum vessel 1 via the insulator 8. The potential of the anode 28 is set to floating, ground, or any positive or negative voltage as required.

A sample substrate 25 (hereinafter, referred to as a substrate 25) provided at an opening 9 below the vacuum vessel 1 so as to face the target 5 at an appropriate interval.
) Is provided. Substrate electrode
Reference numeral 10 denotes a substrate supporting portion 10A on which the substrate 5 is placed, and an extending portion 10B extending downward in the drawing. Substrate electrode 10
A substrate holder 12 surrounds the substrate electrode 10 and holds a peripheral edge of the substrate 25 via an insulator 11 having a vacuum sealing function. The substrate holder 12 is formed so as to be movable in a direction perpendicular to the surface of the substrate 25 (up and down direction in the figure) (moving means is not shown). A shield 14 is provided around the substrate holder 12 via an insulator 13 also having a vacuum sealing function so as to surround the substrate holder 12, and the shield 14 is fixed to the opening 9 of the vacuum container 1. The substrate coil 17 is provided in a coil container 16 fixed to the opening 15 below the vacuum container 1, and is vacuum-sealed with the vacuum container 1. A board coil power supply 24 is connected to the board coil 17. A high frequency power supply 21 and a DC power supply 22 are connected to the substrate electrode 10 and the substrate holder 12.
When only the DC bias voltage is applied to the surface of the substrate 25, the high-frequency power supply 21 is unnecessary, and when only the high-frequency bias voltage is applied, the DC power supply 22 is unnecessary. When a high-frequency bias voltage is applied, the substrate holder 12 is made of an insulating material to shield high-frequency plasma.

An inert gas such as Ar gas is introduced into the vacuum vessel 1 through a gas introduction unit 19, and is evacuated by an exhaust unit 18.
The pressure is kept at about 10 ^-3 Torr.

The temperature control means cools the substrate 25. In the present embodiment, the temperature control means is formed at the center of the substrate supporting portion 10A and the extension portion 10B of the substrate electrode 10, and fits into a through hole opened to the substrate 25 side and the opposite side. Gas introducing pipe 29 to be introduced, an introducing device (not shown) for introducing a cooling gas having the same state as the gas (with Ar gas 1 or the like) charged in the vacuum vessel 1 into the gas introducing pipe 29, and an unillustrated device for controlling the gas temperature It is formed from a temperature control device and the like.

FIG. 2 shows a reference support 10 of a substrate electrode 10 for supporting a substrate 25.
3 shows the detailed structure of A.

The portion of the reference support portion 10A in contact with the substrate 25 is formed in a loose convex shape (accurately, a spherical shape) rising toward the substrate 25 as shown in the figure. This is for the following reason.

As described above, the periphery of the substrate 25 is held by the substrate retainer 12, and the substrate 25 is disposed so that the cooling gas from the gas introduction pipe 29 hits the lower surface. The upper side of the substrate 25 (the vacuum vessel 1 side)
Since the vacuum is about 10 ⁻³ Torr, the central part of the substrate 25 bends by about 100 μm by introducing the cooling gas. On the other hand, the substrate 25
In order to maintain a constant heat transfer coefficient between
It is necessary to reduce the gap between the substrate electrode 10 and the substrate electrode 10 to 10 μm or less, and to make close contact engagement. Therefore, by forming the reference support portion 10A in a convex shape by an amount corresponding to the substrate 25 being bent by the gas pressure in advance, the adhesion between the substrate 25 and the substrate electrode can be maintained.

 Next, the operation of the present embodiment will be described in more detail.

The substrate 25 to be subjected to the sputter film forming process is inserted from an inlet (not shown) of the vacuum vessel 1 and the substrate supporting portion 10A of the substrate electrode 10
Placed on top. In this case, the substrate holder 12 is the substrate electrode 10
Is positioned on the side of the target 5 which is separated from the target. Board 25
Is placed, the substrate holder 12 is moved to the substrate 25 side by a transport mechanism (not shown), and engages with the peripheral edge to hold the substrate 25. After the high vacuum in the vacuum vessel 1 is evacuated by the evacuating means 18, Ar gas is introduced from the gas introducing means 19 and the gas introducing pipe 29 to maintain a predetermined sputtering pressure. The target coil 6 is controlled by the target coil power supply 23 and the substrate coil power supply 24.
And a coil current is applied to the substrate coil 17 so that the two magnetic fields are in opposite directions. As a result, the magnetic field lines shown in FIG.
A cusp magnetic field having a shape like 26 is generated. Next, when a sputtering voltage is applied to the sputtering electrode 4 by the sputtering power supply 20, a high-density plasma 27 having the same shape as the lines of magnetic force 26 is generated from the surface of the tart 5 to the vicinity of the surface of the substrate 25. Next, a DC bias is applied to the surface of the substrate 25 through the substrate holder 12 by the DC power supply 22, or a high-frequency power is applied to the substrate power supply 10 by the high-frequency power supply 21 to further generate a high-frequency plasma on the substrate 25. A bias voltage is applied to the surface of the substrate 25, and the surface of the substrate 25 is maintained at a negative bias potential.
The ions in 27 flow into the substrate 25. At this time, gas introduction pipe
The substrate 25 is controlled and maintained at a predetermined temperature by the Ar gas introduced from 29.

Next, the result of forming an Al material by the apparatus of this embodiment will be described with reference to FIGS. 3 and 4. FIG.

FIG. 3 shows the ratio between the substrate coil current and the target coil current on the horizontal axis, and shows the film forming rate (mm / min) and the film thickness distribution (%) on the vertical axis. The dotted line indicates the film thickness distribution). By increasing the coil current ratio,
The magnetic field lines 26 of the cusp magnetic field are pressed against the target 5, and the region of the plasma on the target gradually moves from a range larger than the outer diameter of the substrate 25 to the center side, and the film forming speed increases and the film thickness distribution increases. The periphery of 25 changes from a thick concave distribution type to a thick convex distribution type at the center of the substrate. Now, set the target film forming speed to 1000 mm / min or more and set the film thickness distribution to ± 5%.
In the following case, the coil current ratio satisfying this condition is 0.95 or more.

FIG. 4 shows the substrate temperature rise characteristics when the coil current ratio is 0.95 at a film forming speed of 1180 mm / min (1000 mm / min or more). The horizontal axis shows the time (S) after the start of film formation, and the vertical axis shows the temperature (° C.) of the substrate 25. After elapse of 20S from the start of film formation, the temperature of the substrate 25 becomes 350 ° C., and unless the substrate 25 is cooled by the temperature control means, the temperature of the substrate 25 continues to rise as indicated by a dotted line, and the film thickness becomes 1.2.
The temperature reaches about 650 ° C. after 60S required to obtain μm. On the other hand, since the melting point of Al is about 650 ° C.,
l There is a problem that a part of the material is melted. Therefore, after about 20 S after film formation, when gas cooling is started by the substrate temperature control means, even after 60 S after film formation starts, the substrate 25 is about 350 S
It is kept at ° C. As described above, by generating high-density plasma up to the vicinity of the surface of the substrate 25 while gas-cooling the substrate, the sputtered material can be turned around steps, grooves, deep holes, etc. on the substrate surface at a low bias voltage that does not cause film defects. In addition to being able to form a film well, heat generation of the substrate and damage due to ions are prevented, and a high-quality thin film can be formed.

In the present embodiment, the target coil 6, the substrate coil 17
Is an electromagnet, but the present invention is not limited to this, and a permanent magnet that generates a magnetic field equivalent to these may be used. In this embodiment, the substrate temperature control means cools the substrate 25.However, the present invention is not limited to this. When the film forming speed is low and the heat input to the substrate 25 is small, the substrate electrode
In order to maintain 10 at a high temperature, the substrate during film formation is heated by a gas medium.

〔The invention's effect〕

As is clear from the above description, according to the present invention, a high ion current flowing into the substrate can be obtained at a low bias voltage, so that the steps, grooves and holes can be sputtered without causing film defects such as voids and blisters. A film can be deposited. Further, since the substrate bias voltage can be set independently of the generation of high-density plasma, the ion energy can be controlled while keeping the amount of ions flowing into the substrate almost constant. Further, since the substrate can be controlled at a constant temperature, the quality of the film can be improved.

[Brief description of the drawings]

FIG. 1 is a vertical overall view of one embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, FIG. 3 is a diagram showing film forming characteristics according to one embodiment of the present invention, FIG. FIG. 3 is a diagram showing substrate temperature rising characteristics. 1 ... Vacuum container, 2,15 ... Opening, 3 ... Insulator, 4 ...
Sputtering electrode, 5 ... Target, 6 ... Target coil, 7 ... Yoke, 8,11,13 ... Insulator, 9 ... Opening, 10 ... Substrate electrode, 12 ... Substrate support, 14 ... Shield , 16 ... coil container, 17 ... substrate coil, 18 ... exhaust means, 19 ... gas introduction means, 20 ... sputter power supply, 21 ...
... High frequency power supply, 22 ... DC power supply, 23 ... Target coil power supply, 24 ... Substrate coil power supply, 25 ... Substrate, 26 ... Magnetic field lines, 27 ... Plasma, 28 ... Anode, 29 ... Gas inlet tube .

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-57-207173 (JP, A) JP-A-61-12866 (JP, A) JP-A-61-221363 (JP, A) JP-A 52-207 56084 (JP, A) JP 52-49992 (JP, B2)

Claims (2)

(57) [Claims] An inert gas such as an Ar gas is introduced into a container evacuated to a vacuum, a predetermined pressure is set, and a cusp is placed between a target and a substrate disposed inside the container. A magnetic field is generated, a first power is applied to the target to generate plasma, the plasma is confined between the target and the substrate by the cusp magnetic field, and a second power is applied to a substrate electrode on which the substrate is mounted. Is applied to generate a bias potential on the surface of the substrate, and the target is sputtered by plasma confined between the target and the substrate by the cusp magnetic field to form a film on the substrate, and the bias potential is applied from the bias potential. Irradiating ions from the plasma onto the surface of the substrate on which the film is formed, and introducing a gas between the substrate and the substrate electrode to cool the substrate on which the film is formed. Sputtering film forming method which is characterized. 2. A vacuum vessel means having an evacuation section and a gas introduction section, a target means having a target surface sputtered inside the vacuum vessel means, and facing the target surface inside the vacuum vessel means. A substrate electrode means for mounting and holding the substrate to be processed, and a first
A first power application unit that generates plasma by applying power of the above-described manner, sputters the target surface to form a film on the substrate to be processed, and faces the target unit side and the substrate electrode unit side. Magnetic field generating means for forming a cusp magnetic field between the target surface and the substrate to be processed held by the substrate electrode means and confining the plasma in the cusp magnetic field; A second power application means for applying power to generate a bias potential on the surface of the substrate to be processed and for causing ions from plasma confined by the cusp magnetic field to be incident on the surface of the substrate to be processed during film formation; Gas introduction means for introducing a gas between a processing substrate and said substrate electrode means and cooling said substrate to be processed during film formation while allowing said ions to be incident thereon. Location.